Correct a typo in the description of interaction between
the TCM and MMU.

Found by inspection.
Signed-off-by: Simon Horman <simon.horman@corigine.com>
Link: https://lore.kernel.org/r/20220609184230.627958-1-simon.horman@corigine.comSigned-off-by: Jonathan Corbet <corbet@lwn.net>